


Behind her Back

by BizarreJoe



Category: Codename: Kids Next Door
Genre: Bathroom Sex, Blackmail, Cuckquean, Cum Swallowing, Cum drinking, F/M, Public Sex, blowjob, female on male blackmail
Language: English
Status: Completed
Published: 2019-03-19
Updated: 2019-03-19
Packaged: 2019-11-24 04:42:31
Rating: Explicit
Warnings: Underage
Chapters: 1
Words: 4,309
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/18161609
Author URL: https://archiveofourown.org/users/BizarreJoe/pseuds/BizarreJoe
Summary: Mushi is tired of seeing her sister getting everything before she does. But no more, she has her eyes on one thing that Kuki wont get before she does. Shes going to take it away right from under her nose. Mushi Sanban is going to steal her sister's boyfriend.





	Behind her Back

**Author's Note:**

> I'm sorry for the lack of updates lately. Things have been crazy down here in venezuela ever since January, and we have been dealing with a mega blackout for the last 2 weeks.
> 
> I wont make it long this time. This story was commissioned by an anonymous commissioner. He likes it, and I hope you do too.

" _Wallabee, how the hell did you let it get this far_?" he wondered to himself as he laid on the sofa. Wallabee Beetles, or Numbuh 4 as his friends called him, was not known for being particularly smart. Still, the fact that he managed to fuck something like this up surprised him more than anything he had done before. He couldn't brush this one under the rug as someone else being an idiot or bad mouthing him. He had allowed it to get this bad and he only had himself to blame.

He could have stopped Mushi at any moment, but she had gotten out of hand, and now, in the middle of the night, it was all going to come crashing down. All he could do as she crawled up to his spot on the sofa was to remember how all of this went so wrong, so fast.

If Numbuh 4 had learned one thing during Grandfather's invasion, it was that Kuki Sanban, Numbuh 3, had actually reciprocated the crush he had for her for so long. Even if they were almost zombified when that confession happened, they both still remembered it and had decided to continue to be together after the ordeal was over.

Whilst he was technically in a relationship with his coworker, it never seemed all that serious. He never took it as such, until one day she invited him over for dinner. He had been to Kuki's house before. None of those visits had seemed quite as serious or daunting as it was now. It was just him going to a friend's house, one that he had a crush on, but a friend nonetheless. Why the mood was so different? Probably because everyone kept insisting that it was a date. His dad gave him an old blazer he used to wear when he was around his age. Abby (Numbuh 5) told him to just act naturally, that girls love honesty… unless it meant acting like a dickhead, in which case he should totally act differently. And Nigel and Hoagie (Numbuhs 1 and 2) just told him to try to not be an idiot. In the end all of them told him to not fuck this up.

When the day started, none of that bothered him. But the closer he was to the Sanban house, the more tense he became. What would happen if he fucked up? Would his friendship with Kuki be over as well as his relationship? He wasn't the kind to make plans, or panic about things not going according them, but by the time he was at the Sanban's door, he was terrified of what could happen behind that door .

He rang the doorbell and gave the widest, most awkward smile that he could make. Of course he was trying to give a confident one, but he wore his feelings on his sleeve, so he could never maintain a facade, even then when Kani and Genki Sanban opened the door and after looking down at him, they let him pass.

Wally felt as if they were evaluating him. Judging if he was even worthy of entering their household. Which made absolutely no fucking sense because he had been here before, they had held company parties, in which his family had been invited, because Kuki's mom was his parent's boss. So he thought that this kind of attitude was a ball of nonsense.  _They know me!_  He thought to himself, failing to grasp what was different. To his credit, he did get the gravity of the situation eventually. It only took him a few minutes, when he was nervously sitting in front of Genki.

He had been fighting hostile adults for years now, yet he had never felt this intimidated by any of them before. If it was because the success or failure of this date was dependant on their, approval,he didn't consider it, as he tried to make small talk with them, without having anything to actually say. With a series of "uhms", "aaahss" and other gaps of vocabulary, he failed spectacularly. Maybe the most embarrassing one was when he said "nice weather today, eh?" That, while it did technically counted as "language", betrayed his nervousness, because he just had come from the outside, so he knew that the gray clouds covered the sky, and that every so often, thunderously announced their plans to become a snow storm.

Wally's smile had never been bigger or more awkward before. At this point all he wanted was for a war to break out or for the ground to swallow him. Anything to make this moment less awkward. Thankfully for him, something less apocalyptic happened to break the tension, he basically got tackled out of his seat when his girlfriend jumped to hug him.

The whole thing was a surprise, she hugged him so hard he was sure something inside him was going to crack, Kuki almost made him fall from the chair, he hugged her back to avoid falling, he took a quick look at Genki before giving the hug back in full. Kuki's mother was smiling, it didn't mean that he was off the hook, it meant thats she liked seeing her daughter happy. And that's when he knew what to do. It was something very easy, because it was what he wanted to do from the get go: he had to keep Kuki happy.

And for a while it worked. It kept Numbuh 3 happy, it kept his parents happy, and it kept him alive and inside the house. He was less tense, knowing that everyone in the house was less hostile seeing Kuki in a good mood.

What he failed to notice, was that that wasn't exactly true. From the stairs, someone else he had forgotten about almost completely. It wasn't every day that he thought of Mushi, Kuki's little sister, who at the moment was looking down on the scenes that unfolded in the lower floor. And she didn't like them one bit.

And unlike her family, she wasn't enjoying Wally's presence a single bit. Or her sister's rather. Because the boy now sitting with her and talking to her parents was just another one in the long list of things that her sister had that she hadn't. And she knew that something this big was coming when her parents asked her to stay in her room for the afternoon.

Why should she? Kuki had the bigger room, she had more toys, and now she had a boyfriend.

 _ **No**_.

She wasn't going to let Kuki get all of the attention again. This is something she was going to get all to herself. And she already had an idea of how to do it. All she needed now, was to wait for the right moment to strike.

That moment, was dinner.

The Sanbans were a very particular family. While they weren't "right" or too wealthy, they were a part of the upper middle class, they had a big house, multiple cars and worked for a big corporation. And yet, they always seemed to avoid spending any money unless it was totally and absolutely necessary. They did not pay for heating, they did not pay for cable, and barely paid for internet. And in that same vein, they only bought what their family needed, like a table for four, well, not since the last one melted in a certain, unfortunate thermostat "accident".

It was the reason Mushi had been asked to stay in her room, and the reason why her parents were surprised to see her among the people present when her father Kani was setting the table. He demanded that she left the place immediately, Mushi put her best pair of puppy dog eyes as she begged to stay and eat with the rest of the family.

Seeing an opportunity to earn more approval from the Sanban patriacs, Wally responded to her pleas and said "There's no problem Mrs Sanban, she can stay and eat with us. She can sit on my legs".

Genki told him to "Suit yourself, if that's what you want"

And it was then when  _ **The Troubles**_  actually started. The mild discomfort that he felt on his legs for the duration of the meal wasn't a problem, not really. The problem was something different. You see, both Sanban sisters shared one particular quirk. They both went "light on clothing". Usually, they only wore three pieces of clothing. A sweater, an undershirt and spats. He has seen all three on Kuki, it was her style, and since Mushi had strange, deranged way of looking up to her sister, she wore it as well, but something was different. He felt too much.

Even with his pants on, he could feel that she was missing one piece of clothing. The spats that were supposed to be under her long sweater were missing. Weirded out, Wally looked down, Mushi looked up at him and gave him a smug smirk as she pulled up enough of her sweater to show him that she indeed was wearing nothing at all under her clothes.

Wally turned as red as a beet and quickly sat as straight as he could so fast that Genki and Kani only saw a blur when he moved. He gave them his best awkward smile before they decided to open conversation again.

"Wallabee, is anything wrong?" asked Genki

Shaking his head as quickly as he could, Numbuh 4 answered with "Nothing at all, nope, nothing at all, I mean no".

Genki shrugged it off as just kids being weird. And continue to make small talk with the same kind of subtlety and tension that she would use to conduct a job interview. But Wally wasn't listening to her. He couldn't focus on anything other than trying to appear as if the girl that was sitting on his lap wasn't rubbing her bare butt all over her his crotch.

Every single minute that passed, hiding it became harder, because every single minute that passed had Mushi get more intense, and it made his penis harder and his face redder. He was looking at every single person at the table as if any of them could find out at any minute.

When you join the KND, you're trained for a lot of things, but none of them were even close to being similar to this. The ministrations of the girl on his lap alone were making him feel something that he had only experienced once before. He knew what was coming up, so at the first chance he had, he quickly stood up and asked

"Can I go to the bathroom please?"

Kani told him "at the end of the hallway by the stairs, you can't miss it". He may not like the kid the much, but he knew what his wife's cooking could do, and nobody deserved that.

The boy ran up to the bathroom, and just like that Mushi was left alone with her family. But she didn't look as someone who had been rejected. As she looked at the boy basically running to the bathroom, she had a knowing smirk, because everything had gone according to plan.

…

In the bathroom, Wally was looking at the mirror after having splashed some water on his face. He was very close to hyperventilating.  _What the fuck was that kid thinking!_ He thought to himself, almost panicking, and he had a reason to panic, what if anyone saw that?

What if Kuki's mom saw it? Hell what if Kuki saw it? She would have been heartbroken, it could have been the end! Mushi was left alone with her family. But she didn't look like someone who was just rejected by someone, no, she looked at the boy practically running away with a smile on her face. The smile of someone whose plan was going just as expected.

He closed his eyes and steeled himself, he had decided. He was going to go down back to the table, pull her aside and "I'll go tell her".

"You'll tell me what?" said a acute but very familiar girly voice behind him.

The screech he made was so girly that anyone may think he was back at St. Rita's. He quickly reached inside his blazer to look for a weapon, completely forgetting that due to the occasion, he actually came unarmed. Still, he was the best fighter he knew about, so he turned back to face his intruder… only to find Mushi smiling at him.

"Wot the hell are you doing here!" He said, maybe a bit louder than he should have, all things considered.

"You know, if you keep screeching and yelling, mom and dad are going to wonder what is happening here" She said every single word with a knowing weight and a wide grin. Wally knew about the kind of people that smile like this… those were people with evil plans. "You wouldn't want that, would you?"

Frowning, Wally asked "What are you doing here, heck how you even get in here!" barely above a whisper. A very angry whisper.

"I came through the window…" she said, pointing at it "And I came to see you…"

"Why would you-" He couldn't even finish the sentence before the girl came dangerously close to him and looked up to his face.

"Saaaay Wally… has my sister shown you that?"

"What?!" he asked, legitimately not knowing what she meant.

"What I showed you at the table, you didn't look like you knew what it was" She slowly lifted her sweater, until her pristine, hairless sex was in full display "Has my sister never showed you her kitty?"

"Kitty? What are you even" he stammered, before rising his voice again "cover yourself already!"

Mushi's grin grew into a full blown smile, this was the best outcome that she could have hoped for. For once, she was grateful because her sister had one thing that she didn't: Modesty.

Still lifting her sweater above her waist, she walked up to him slowly. "Has she really never shown you this? She's such a bad girlfriend"

"Don't talk about her like that" He said, raising his fist. Something that Mushi didn't even acknowledge, she knew exactly what was going to happen here, he didn't. But she had him dancing on her little finger already.

"Why not? You guys have been going out for months, and she hasn't even shown you this?" She was getting really close, but he couldn't bring himself to push her away, his face was sweating, and his dick was getting really hard. "Good girlfriends do it all the time, looks like you still need one of those"

One she was face to face with him, she dropped her sweater. He asked "What do you want?"

She lifted herself, and whispered a single word up to his ear, "You."

He tried to say "And how do you plan to get that?" but only got halfway through, before she grabbed his crotch, and started rubbing him through his pants.

"And it looks like there is at least one part of you that wants  _me_ " She was the devil, or thats what her smile made Wally think, but he did nothing to stop her, the heavy petting felt too good.

Without a single word more, she kneeled down, and unzipped his pants. 4 was now between a rock and his hard cock. This feeling wasn't exactly new, but it was the first time that it fogged his mind so much. So much that he didn't do or say anything when she pulled his cock out and started licking it.

What he felt when her tongue went all the way up his shaft was hard to describe, what he felt when she started lapping around his cockhead was totally indescribeable. He pulled his head up and tried his best to contain a moan, but couldn't help but let it slip through as she began to facefuck herself on him, driving her face deep into Numbah 4's pelvis. She loved the feeling of going up to his tip and then slamming her face up to his crotch, she was enjoying herself to no end, but this blowjob was about to be over. It's not as if she had done it before, but as she massaged his balls, she felt them tensing.

Not even all the preparation in the world would have been able to prepare her for what happened. He grabbed her head and kept it stuck to his crotch as he dumped load after load in her mouth.

His moan was so loud that it was impossible that the Sanban's didn't heard it. Mushi herself just pushed herself away and closed her mouth immediately to avoid spitting out a literal mouthful of cum.

It was such a strange taste. Salty but not at all gross, it was thick but still liquid, like warm yogurt. It was hard to swallow it all in one go, but she had a satisfied expression on her face as she took long hard breaths. She showed her mouth, and was ready to say something but someone spoke first.

"Kid! Are you okay? You sounded like you were in pain" Said Mushi's dad from the other side of the door. "Look, I know what my wife's cooking can do so, take your time, but, the storm is getting bad, so we called your parents, and told them you were going to have to spend the night here"

Numbuh 4 had been in dire situations before. He had fought again dozens of teenagers, literally hundreds of adults, and dozens of rogue KND operatives, but he had never felt as much fear as he felt at that moment, he had his five inches of cock hanging out in front of this man's daughter, with her mouth smelling of something that just came out of his dick.

If Kani opened the door Wally was dead, and he was perfectly aware of that, so he got his cock inside his pants and zipped them up. Mushi looked seriously disappointed. But men will be men, so she stood up. Came up to his ear and told him. "If you want to feel better than this, wait for me on the sofa tonight at 12"

He had so many questions, feeling better than this? He doubted that it was possible, but he nodded and said that he would get out first.

Aside from a couple of weird looks, no one at the table seemed to think that something out of the ordinary happened in the bathroom. And that was good, Wally was doing his best to not look like someone who just facefucked their youngest daughter in the bathroom, and judging by the fact that the rest of the dinner went as well, and that when night came he was offered the guest room, some may say that he succeeded, but while lying on bed on nothing but his underwear he sure didn't feel like it.

He had been doing something that, admittedly, he didn't do a lot of. He was thinking, thinking about what to do… does he go to the living room to wait for Mushi and do whatever she wanted to do? Will he really go down and willingly cheat on the girl that he had a crush on for so many years?

Well, yeah. His dick won in the end, because he was on the sofa waiting for Mushi 5 minutes before midnight. his brain tried it's very best to get him out of there, but once the clock marked 12, it was as if the kid materialized besides the sofa.

"Heeeeeeeeey Waaaaaaaaally" said her girly voice, piercing through his ears like a drill. "you're here! sooooo you really want to see what a good girlfriend can do?"

…

And so we are back here, with Wally cornered against the armrest, and a very nude Mushi crawling towards him. His heart beat as fast as a hummingbird's, his mind raced, but every thought came back blank. he felt his heart in his throat, it was like his whole body was begging him to run away, but he was completely unable to do so.

And it wasn't until Mushi was right in front of him, with her lips right on his, that he realized that he wasn't going to be able to punch through, or run away from this. He was going to have to go all the way with this, so he just let it happen. The kiss… and what happened afterwards.

He took off his boxers the second that she asked him to, and she licked her lips when she saw that he was hard and dripping for her. She licked some precum off his tip as she looked into his eyes. She didn't need to try hard, she had him wrapped around her finger already.

But still, she enjoyed watching him squirm. So she cleaned his circumcised cockhead, before moving up, and straddling him, she saw his panic grow as she descended, but she stopped right as his tip touched her entrance.

"Waaally, are you ready? Are you ready to make me your better girlfriend?"

"I'm n-" she didn't let him answer, instead, she lowered herself forward. Enough to bring him inside her, but not enough to fully penetrate her. His groan was music to her ears, enough to soothe the pain that she felt as she lowered herself on his member.

She smiled through it, now she had something else that Kuki didn't have, her boyfriend's virginity. And as she started to move, that fact became clear. He groaned and moaned with every move, every new sensation was like lighting striking their brain, their bodies and their souls. It was a new feeling for both of them. Every sound was a different melody to her ears.

With a single command she ordered him to start moving, and when her did, the real fun began. Both kids were sweaty, both were moving in wild unexperienced ways, and both of them didn't care about any of that. They were so lost in their own passion, that they forgot everything around them, they even forgot that they were supposed to be quiet.

Because once Wally shifted his position, becoming the one on top, she started moaning louder than ever, the sound filled the room, but as he just kept pumping, the pleasure was just too much to stop. He started to feel that something coming up again, and he said as much. Mushi only hugged him closed, and told him to keep it inside, before kissing his lips even more wildly than the previous time.

As their passions kept rising, their minds went more and more blank, and as their pleasure reached its peak. Wally came, he came loads and loads inside of her diminutive body. She felt her insides move to accommodate so much cum, it was a feeling like nothing she had felt before, it was as if all the emotions she had felt as she got fucked all combined to attack every single inch of her body. It was too much, way too much, it made her go over the edge and have what would be her first, and for a while biggest orgasm.

With the biggest feeling of satisfaction, and no a single drop of mental power to discern why, Mushi fell asleep. Exhausted, Wally soon followed, landing almost on top of her.

They had no energy to bask in the afterglow, and honestly, he felt like he could sleep through the next two days, but he awoke when someone slapped him in the face.

"Oi! What gives!" he said, rubbing his cheek

"Stand up you brute, I can't move" Mushi's voice, came from beneath him, and didn't sound particularly amused.

Looking at the naked girl, he quickly moved back to his spot near the arm rest. Panicking, he looked around the room, a look to the clock on the wall revealed that it was merely two in the morning, a couple of hours since he came here.

"Oh crap, we are naked" He said, his fear increasing as the memories of what they had done came back in a massive wave "Oh crap, your parents, what if they heard us! What if Kuki heard us? We are so dead!"

"Relax, I slipped something in their drinks, someone could tear the house down and even then they wouldn't wake up"

"You did… what?"

"They won't bother us Wally"

"You planned this?"

"You could say that... say… it will still be a while before they wake up, so, wanna go again?"

It took all of his will to say "No", it made her sad to be rejected like this, but she had a consolation prize. The sight of his delightful booty as he put his underwear back on and the sheer amusement of seeing him trying to come up with a reason why this was a bad idea and being completely unable to name one.

She was happy still. And even when he said that "this is the only time that I'll ever let this happen" before going up the stairs, Mushi new better, she could see the future clearly. Him with his hand on her tight ass while they watched a movie with Kuki, him passionately making out with her behind the bleachers as Kuki waited for him outside of school, him furiously fucking her on his wedding day, as Kuki expected her loyal husband at the altar.

Yes. She told herself, as she rubbed her belly full of cum, her future with him was clear, and she was happy with it. Because Kuki may have his love, but Mushi had her man.

And she wasn't going to give him up, any time soon.


End file.
